I. Field of the Invention
This invention relates to additives for lubricants made by treating a Mannich condensation product of a phenolic compound, aldehyde and amine with elemental sulfur. It also relates to lubricant compositions containing such additives.
II. Prior Art
The use of nitrogen-containing Mannich condensation products derived from phenols, aldehydes and amino compounds as additives for lubricants and normally liquid fuels is known to the art; see for example, U.S. Pat. Nos. 3,368,972 and 3,649,229. The formation of such additives using Mannich condensation reactions involving sulfur-containing reactants is also known to the art, see for example the following:
______________________________________ U.S. PATENTS ______________________________________ 3,335,201 polysulfide-containing condensates 3,368,972 sulfur-bridged phenol condensates 3,649,229 sulfur-bridged phenol condensates 3,458,495 phospho-sulfurized hydrocarbon- treated Mannich condensates 3,539,633 thiourea condensates 3,600,372 CS.sub.2 -treated Mannich condensates 3,649,659 sulfonic or sulfuric acid-treated Mannich condensates 3,741,896 sulfurized phenol-treated Mannich condensates ______________________________________
Treatment of acylated polyamines with elemental sulfur is also known to produce useful ashless dispersants for lubricating oils. See for example, U.S. Pat. No. 3,390,086.
The increasing demands for improved effectiveness of lubricants and normally liquid fuels with respect to engine emissions and economy as well as the increasingly severe conditions under which such materials are expected to perform has led to a continuing search for new additives. The present invention resides in the discovery that treatment of certain nitrogen-containing Mannich condensates with elemental sulfur produces additives for lubricants which endow the lubricant with improved oxidative and thermal stability. This allows greater latitude in the conditions under which these additives and compositions containing them can be stored and used. The inventive additives are particularly useful in lubricant compositions for use in automotive and truck automatic and manual transmission fluids, hydraulic fluids, hydrostatic fluids, power steering pump fluids and the like.